Gambit has some syntax to call functions in the host language (C/Python/Ruby/etc). That syntax is what is used to call Javascript functions that exist in the context where the compiled script is executed (window/node). As far as using stuff like ES6 style imports and the like, there is a project on Github called gambscript but it isn't complete as far as I can see. Someone out there can get closer but I know it isn't me.